Amazon said Friday that it will spend more than $1 billion to buy its corporate headquarters in Seattle from Microsoft co-founder Paul Allen’s investment firm.

The world’s largest Internet retailer plans to buy 11 buildings, comprising 1.8 million square feet of corporate office space, for $1.16 billion. Amazon said it expects to close the deal in the fourth quarter.

Amazon had been leasing the space. But at the end of August, Allen’s Vulcan Real Estate, part of his Vulcan investment vehicle, put the buildings in Seattle’s South Lake Union area up for sale.

Allen, who co-founded Microsoft with school friend Bill Gates, has been the central figure in revitalizing the South Lake Union neighborhood, which was a semi-industrial wasteland until recently, but is now a thriving center for tech firms and features a number of fashionable restaurants.

Amazon already has plans to build new offices nearby to house its growing staff.